Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany.
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, 565-0871, Osaka, Japan.
Metab Eng. 2019 Sep;55:239-248. doi: 10.1016/j.ymben.2019.07.009. Epub 2019 Jul 22.
Poly-γ-glutamic acid (γ-PGA), which is produced by several Bacillus species, is a chiral biopolymer composed of D- and L-glutamate monomers and has various industrial applications. However, synthesized γ-PGA exhibits great structural diversity, and the structure must be controlled to broaden its industrial use. The biochemical pathways for γ-PGA production suggest that the polymer properties molecular weight (MW) and stereochemical composition are influenced by (1) the affinity of γ-PGA synthetase for the two alternative glutamate enantiomers and (2) glutamate racemase activity; hence, the availability of the monomers. In this study, we report tailor-made γ-PGA synthesis with B. subtilis by combining PGA synthetase and glutamate racemase genes from several Bacillus strains. The production of structurally diverse γ-PGA was thereby achieved. Depending on the PGA synthetase and glutamate racemase origins, the synthesized γ-PGA contained 3-60% D-glutamate. The exchange of PGA synthetase changed the MW from 40 to 8500 kDa. The results demonstrate the production of low-, medium-, and high-MW γ-PGA with the same microbial chassis.
聚γ-谷氨酸（γ-PGA）是由几种芽孢杆菌产生的手性生物聚合物，由 D-和 L-谷氨酸单体组成，具有多种工业应用。然而，合成的γ-PGA 表现出很大的结构多样性，必须控制其结构以拓宽其工业用途。γ-PGA 生产的生化途径表明，聚合物的性质分子量（MW）和立体化学组成受（1）γ-PGA 合成酶对两种替代谷氨酸对映异构体的亲和力和（2）谷氨酸消旋酶活性的影响；因此，单体的可用性。在这项研究中，我们通过组合来自几种芽孢杆菌的 PGA 合成酶和谷氨酸消旋酶基因，报告了利用枯草芽孢杆菌定制 γ-PGA 的合成。从而实现了结构多样化的 γ-PGA 的生产。根据 PGA 合成酶和谷氨酸消旋酶的来源，合成的 γ-PGA 含有 3-60%的 D-谷氨酸。PGA 合成酶的交换将 MW 从 40 至 8500 kDa。结果表明，相同的微生物底盘可以生产低、中、高分子量的 γ-PGA。
